Torque measuring device



1952 s. c. COCKRELL ETAL 2,614,417

TORQUE MEASURING DEVICE Filed Oct. 20. 1949 2 SHEETSSHEET 1 FIG. 1.

Qwuwwbom s. c. COCKRELL F. F. GLASGOW my v 1952 s. c. COCKRELL ETAL2,614,417

TORQUE MEASURING DEVICE Filed 001". 20. 1949 2 SHEETS-SHEET 2 FIG.3.

FIG. 4.

s'. c. COCKRELL F. F. GLASGOW Patented Oct. 21, 1952 TORQUE MEASURINGDawes sinibra o. Cockre ll, Washington, 1). o ana Forrest Glasgow,Wilmington, Del.

Application octoberzo, 1949, Serial No. 122,562

' (01. 7a -1s7 (Granted under the. act of Marsh 3, as

Claims.

1 1: relates to a method and inechrmgan recording torque such qu red torotate ashaftor like rc-- obgebt through a series oi revolutions object"f, the presentinvention sm pr d improved apparatuslqy means "the torquerequired to rotate a shaft can be ngiea'suredandrecorded I urthe'robject is to provide a method and m re-r1 measuring and I recording theapplie djto a niotor driven object in calib'rated units: by measuringand recording the currentsiipplied toth motor. l 1 Still a mi-trierobject ,bf t e, present inven= tion is to lds figs as 1 es b sh rare ief r v ?q :2, r ga din the recorded torql'ie measurements s a d many a:theattridnt ea: this invention will be readilgi ap= the same becomesbetter under p a I enfce to t'he renew ng detailed a iption'whnconsidered in connection vkiith the accompanying drawings wherein:

F is a yiew in elevation of a; portion of oi-quameaspim apparatus; 1g, 2illustrates in diagrammatic form the electrical system pf the torqueineas 'aratus according to the preferred emh le a r a p rspective Viewof the recordin plbyd in 'collncti'oll with the presnr' ,n 415a viewinsection or afragme ta y portion'of a nose fu'ze having an armingsorewwhose torqueis to be measured and recorded by pparapus of the presentinvention asme sore ef'd and withdrawn from the fuze hon r g herebytoarmthe fuze.

Referring now to drawings in which like mmerals of reference areemployed to designate like parts throughout the several views, there isshown in Fig. 1, a base l0 having upstanding vertical walls Hand l2, anadapter l3 and a housing l4 secured to the base. Jourfialed in the"'p'staridmg wa ls In and I2 s a shaft I5 ca iigi. a caubratmg drum I6or a predetermeasured diameter sueh, forieliaihple s 2 i'r i the drumBeing seeur'eajfi tli shaft l m ime -hem lii a- .Thfiha t i5 isjproviddwith a tubular couplingi] :seoured on one end of thefsh aftand a spurgear l8 si ieq; Q 1 rdp'nds iq wi l. ilif g u is provided with alongitudinal slot 45 into which yidemeans for calibrating the curaniended April '30, 1928 370 0. "G. 757) extending radially ifrpm thescr w of the nose fuse, generally designated zfi wh h produce a torquein gear l8 which is in mesh In lma rla e n 9a t no e.v w ch iss i q raio is I as fied. Y? i F r ii iin a n the 'as of t e orede cr beqmii per. er e h we 26 fora bomb or ni ne, as the ea's may lie, itlisdeterrnined velocity wh-erelo y the Suflicbiriji of the impeller blades(not slifovrn) to rotate impeller shaft at this velocity during the freeflight of the bomb or mine in actual use may be ma ly-ea.-

7 T thi and i fiiz 45 s b isi fi rbi idii s r hiv u is he. u l i ls eblati n w r e 9. ai n 9 W A" s h tha the motor 29 may make drivingconnection-s witli 'the ii 1 i e .be m ht ma ie r c 4 rentmotor 29.Motor 29 is supported on top of usin Wh q h s l fica p n a.. ii iimounting a pair of yarfiahle resistors, and

. p n: ef -0n i' hs' a: and 3. 4m

connecting batteries 34 and 35 respeotively infco h Ope tin c cuit o lEi.2. ait i. th it sies have been-connected to the panel a re ing; doublepole double throw s witch136 ,for=d ingthe motor in opposite directionsan d 'p rs of plug conneetions' 31,38; and 3}! foroonnecting batteries,34, 35 a nd recording an meter M into the circuit of 2 through panel31'.

Before proceeding with a detailed description of the. 'elec'trioal.system shown in Fig. 2, it'may] be of assistance; inthe comprehensionoithe inkventionzito recall that a permanent magnet di rect currentmotor is employed for driving the impeller shaft 41 whose torque is tobe measured. In such a motor, the torque on the motor shaft may beexpressed mathematically by the equation:

T=KI wherein A graphic ammeter 4|, such as shown in Fig. 3, is connectedin series with the motor and as varying torques are applied to the motorshaft, the current I flowing through the ammeter will varyproportionally as the load on the motor. In order to calibrate theammeter so as to directly measure the torque such, for example, asinchounces, a series of weights 24 such, for example, as 1, 2, 2, and 5ounces are provided.

The ammeter 4| is calibrated by removing all weights ,24 from support23, disconnecting the arming screw 41 from coupling I1 and closingswitches 33 and 36 to operate the motor with no load on coupling [1. I 7

With the motor operating at no load, a current is drawn thereby toprovide a torque sufficient to overcome the friction, windage, and otherlosses of the driving system for shaft I5. This current is indicated bya displacement of the recording pen from the left, border line 54 onthe-recording tape. It is desirable, however,'for zero or "fno load,that the pen follow border line 54 as a reference line whereby the penwill havethe full width of the tape for torque meas urement of variousobjects to be tested within a rangeof to 10 in.-oz., for example. Thisis accomplished by means of a compensating circuit including battery 34,variable resistance 42, and switch 32. In the use ofthe compensating circuit'to move'the pen to the reference line 54, switch 32 is closed andresistance 42 is adjusteduntil the current supplied to meter 4| is ofzero value thereby to position the pen on the reference line 54. g

Assuming that the no load losses do not vary when different loads areapplied to shaft l as by different objects to be tested, to calibratethe tape to inch-ounces, it merely becomes necessary to measure andadjust the current required to provide the torque to elevate one knownweight 24 on cable 22 and drum It. This is accomplished with all weights24 removed from support 23 and with the arming screw 41 disconnectedfrom coupling [1, as aforementioned. A 5 ounce weight, for example, isthen placed on support 23 and the variable resistance 55 is adjusteduntil the recording pen stops on the line 56 which is the center orfifth line from the reference line 54, and thus indicates a torque of 5inch-ounces, the drum being of 1 inch radius. The other divisions orlines on the tape, being equally spaced thereon, in like manner,indicate torque units in inch-ounces of 0 to inch-ounces as read fromleft to right on the tape The circuit of Fig. 2 is,in effect, a bridgecircuit having motor 29, batteries 34 and 35, and variable resistor 42as th arms thereof, and having'meter 4| and variable resistance 55 asthe center leg of the bridge. Thus, when the bridge is balanced byadjustment of resistor 42,110 curv 4 rent flows through the meter andthe pen is positioned on reference line 54. There is also no currentthrough the variable resistor '55 when the bridge is balanced and henceadjustment of the resistor does not disturb the balance of the bridge.When the bridge is unbalanced as additional current is drawn by themotor to satisfy the torquerequirements of the load, or object undertest rotated thereby, a current flows in the center leg and is dividedbetween the meter and resistor in accordance with the adjustment of thelatter. When the load is removed, the pen is again restored to referenceline 54, regardless of a calibrating change in the adjustment of themeter sensitivity adjusting resistor 55, for the aforementioned reasonthat no current is supplied to the meter when the bridge is balanced.

It will also be understood, of course, that. when desired, the pen maybe operated from any other zero reference line merely by operating thebridge circuit with an initial unbalance.

When it is known that different production groups of fuzes should notrequire operating torques in excess of, 3, 7, and 9 inch-ounces, forexample, and when it is desired to accurately ,determine theaccept-reject condition of these fuzes, each of the torques 3, 1, and Smay be calibrated with respect to the tape, by using 3, '7, and 9 ounceweights as in. the case of the calibration of the 5 inch-ounces torqueaforedescribed, inorder to determine the deviation, if any, of the penfrom the third, seventh and ninth lines on the recording tape. Whenthereis a deviation, a line corresponding to the true torque valueisscribed onvthe tape. Thereafter, all weights 24 are removed fromsupport 23 and a fuzej to be tested is mounted on adapter l3 and thescrew shaft 4'] thereof connected to coupling IL' With switches 32, 3'3,and 36 closed,'the lat ter switch being closed in the proper directionto withdraw the arming screw 41, a torque record such as the curve 5! isproduced for each .fuze tested, curve 51, for example, indicating anacceptable fuze in which the operating, torque therefor in no caseexceeds the anticipated maximum torque of 5 inch-ounces. 1

The reversing switch 36 is employed to reverse the direction of rotationof motor 29, and therefore the direction of rotation of shaft [5,whereby the weights 24 and support 23, and shaft 41 1 may be restored totheir initialpositions.

Obviously many. modifications and variations of the present inventionare possible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

The invention described herein may be manue factured andused by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent ofthe United States of America is: V

1. Apparatus for measuring and recording the torque required to rotate arotatable object com-v prising a first battery, a constant field directcur rent motor having a shaft extend therefrom,a circuit for connectingsaid motor to said battery for operating said motor, an ammeter in saidcircuit and having a recording pen, adapted to be moved from a nullposition variably in accord ance with the value of current supplied tothe motor as the motor operates, a second battery, a

variable resistance -connected in second battery across said ainmbattery being arrange'd't ap I ammeter in opposition t H the po'te wui'ereto by said first battry'wherebysaid rec rm ingpen is moved to,said null position whenthe resistance is variej V tials into equality,means detachably mounted on said shaft for applyinghtorques,ofiknownvalue to saidmotor to calibr'ates'aid ammeter, and driving connectionsfrom 'isaid' motor-"te said rotatable object for applyin the-tor ued theobject to the motor wherebyzthe recording pen is moved away from saidnull position variably in,

accordance with the current supplied to the mo to'r. h a q 1172.; Inapparatusror measuringlgand recording thei'torque required to rotateshaft, the geombination of afirst battery, afconstant field directcurrent motorfmeans for connectin said motor toltheshaftflto be tested,acircuitifor connecting said motor to said battery "for operating saidmotor, an ammeter in said circuit in series with said motor andsaidbattery and having a moving graduated tape and a scribing penadapted to be moved from a null position variably in accordance with thevalue of current supplied to the motor as the motor operates, a secondbattery, a first variable resistance connected in series with saidsecond battery across said ammeter for applying a potential to theammeter in opposition to the potential applied thereto by said firstbattery, said first resistance bein varied to bring said opposingpotentials into equality thereby to restore the pen to said nullpositiorna drum having a predetermined diameter, drivin connections fromsaid motor to said drum for rotating said drum when the motor operates,a cable secured to said drum tape as the predetermined torque value hasto the maximum torque to be recorded on the tape.

3. The method of utilizing a constant field direct current motor tomeasure the torque required to rotate an object under test comprisingthe steps of measuring the current-required to operate the motor at noload, nulling the measured no load currentwhile maintaining said no loadcurrent to the motor, applying a deviceof known torque to the motor,measuring the value of the current in excess of said nulled currentrequired to operate the motor while the known torque device is appliedthereto, removing the known torque device from the motor and couplingsaid object thereto in lieu thereof, rotating the objectby the motor,and measuring the value of the current in excess of said nulled currentrequired to operate the motor with said object coupled thereto wherebysaid measured excess current values may be compared and the torquerequired to rotate the object may be measured .as a proportional valueof said known torque according to the ratio of said current values.

,4. The method of measuring and recording the torque required to rotatean object under test bringjsaid opposing poten 6 direct current moto'ratno load, operating recordin meter by the no load current of'the motor,milling the current through the meter to v operating current whereby thepen is moved from said reference line to a position-at a'-distanceproportional to said torque, scribing a second referenc'e line onf't'he' tape corresponding to said moved position of the pen, removingsaid known torque device from the motor and coupling'said objectthereto, rotating the object bytne motor whereby the operating currentthereto creased above the no load current in p ion; to'the torquerequired to rotatefthe obi c and operating the meter'on said lastnamedincrease; inmotor operating current whereby tne'pen is moved fromsaid first named reference line "variabl'yin accordance with the torqueapplied to't'he motor by said object and the record of the pen on thetape indicates comparatively with respect to said second reference linethe torque required to rotate the object as a proportional value of saidknown torque.

5. The method of comparatively measuring known and unknown torquesapplied separately to a constant field direct current motor whichcomprises the steps of operating the motor at no load. operating acurrent responsive meter by the current required to operate the motor atno load, nulling the no load current through the meter while maintainingthe no load current to the motor, operating the meter by the currentrequired to operate the motor with said known torque applied theretoless said no load current, and operatin the meter by the currentrequired to operate the motor with said unknown torque applied theretoless said no load current whereby the unknown torque may be measured asa proportional part of the known torque according to the ratio of saidmeasured currents.

6. The method of measuring and recording the torque required to rotatean object under test comprising the steps of operating a motor at noload, operating a pen recording meter by the no load current of themotor, nulling the no load current of the motor through the meter torestore the pen of the meter to a first reference line on the tape ofthe meter while maintaining the no load current to the motor, applying adevice of known torque to the motor whereby the operating currentthereto is increased above the no load current of the motor, operatingthe meter on the increase in motor operating current Whereby the pen ismoved from said reference line to a position at a distance proportionalto said torque, shuntin a proportionate part of the increase in motoroperating current past said meter whereby the pen is adjusted on saidtape into registry with a second reference line thereon spaced from saidfirst reference line a distance corresponding to the known torque of thedevice, removing the known torque device from the motor and couplingsaid object thereto, rotating the object by the motor whereby theoperating current thereto is increased above the no load current inproportion to the torque required to rotate said object, and operatingthe meter on the last named increase in operating current whereby thepen is moved from said first named reference line variably in accordancewith the torque applied to the motor by said object and the record ofthe pen on the tape indicates comparatively with respect to said secondreference line the torque required to rotate the object as aproportionate value of said known torque.

7. Apparatus for measuring the torque required to operate a devicehaving a rotatable member comprising, in combination, a motor, a shaftextending from said motor and detachably engaging said rotatable member,means mounted on said shaft for producing a torque of known value, firstcircuit means for energizing said motor, a current measuring deviceconnected in series in said first circuit means, second circuit meanshavinga variable resistor and said current measuring device in seriestherewith, means for energizing said second circuit means so as tooppose the current flow of said first circuit means through said currentmeasuring device, and adjustable shunt means for said current measuringdevice whereby the variable resistor is adjustable to null the currentrequired to operate the motor when said rotatable member is disengagedand said torque producing means is inoperative and whereby said shuntmeans is adjustable to divide the current between the shunt means andthe current measuring device when said torque producing means isoperative to produce a torque of known value.

SANFORD C. CO CKRELL.

FORREST F. GLASGOW. I

REFERENCES CITED The following references are of record'in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,449,458 Sutermeister Mar. 27,1923 1,939,067 Legg Dec. 12, 1933 1,979,340 Norman 7 Nov. 6, 19342,269,584 Eldridge Jan. 13, 1942 2,441,608 Warner May 18, 1948 2,511,178Roter June 13, 1950 2,544,400 Sourwine Mar. 6, 1951

